1. Field of the Invention
The present invention relates to a method of producing non-oriented magnetic steel plate having high magnetic flux density and uniform magnetic properties through the thickness direction.
2. Description of the Prior Art
With the progress in recent years of elementary particle research and medical instruments, there is a need to improve the performance of devices utilizing magnets which are being used in large structures. There is also a need for materials which exhibit a high magnetic flux density in a low magnetic field to use as magnets in direct current applications and as shielding against magnetic fields. The further increase in the size of structures has also brought a demand for steel in which the magnetic properties have a low variation, and especially for steel plate having uniform magnetic properties through the thickness direction.
Numerous electrical steel sheets having good magnetic flux density have been provided, especially silicon steel sheet and electrical mild steel sheet. However, with respect to their use as structural members, problems with the assembly fabrication and strength of such materials has made it necessary to use steel plate. Among the electrical steel plate which has been produced so far is that using pure iron components, as in JP-B No. 60(1985)-96749.
However, the increasing size and performance of the devices concerned has brought with it a strong demand for steel materials with better magnetic properties, especially a high magnetic flux density in a low magnetic field of, for instance, 80 A/m. With the known steel materials it is not possible to obtain stably a high magnetic flux density in a low magnetic field of 80 A/m. In addition, the practical problem of variation in the magnetic properties of the steel is not addressed, particularly with respect to the uniformity of the magnetic properties through the thickness of the steel.
In U.S. patent application Ser. No. 07/368,031 now U.S. Pat. No. 4,950,336 (EPO Ser. No. 89111463.9) the present inventors proposed a method of producing non-oriented magnetic steel plate having a high magnetic flux density.